This study examines the safety and possible utility of using stimulant medications as substitution therapy in cocaine users. Specifically, we are examining the drug interactions between cocaine and dextroamphetamine in a cocaine-using population. This is a Human Laboratory Phase II safety study being conducted in conjunction with Phase III Clinical Trials evaluating the hypothesis that dextroamphetamine prescription will reduce the abuse of cocaine in dependent patients. Male and female subjects with histories of recent cocaine abuse receive two doses of dextroamphetamine (placebo or 30 mg) as a one-hour pretreatment before one of two doses of cocaine (placebo or 96 mg intranasal). Therefore, the study design was a placebo-controlled 2x2 factorial examining the effects of each drug alone and the two in combination. However, human safety issues required that subjects receive each drug alone first, before the combination was administered. The study is nearly completed but the data have not yet been analyzed. However, important to the hypothesis has been our experience that no clinically significant side effects or alterations in cardiovascular functioning have occurred suggesting that at least moderate doses of dextroamphetamine and cocaine can be safely combined. Final data analysis examining whether dextroamphetamine altered the abuse potential of cocaine should proceed at study completion in approximately two months.